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// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
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package org.apache.juneau.utils;

import static org.apache.juneau.internal.StringUtils.*;
import static org.apache.juneau.internal.ThrowableUtils.*;

import java.text.*;
import java.util.*;
import java.util.concurrent.*;

import org.apache.juneau.*;

/**
 * Wraps a {@link ResourceBundle} to provide some useful additional functionality.
 * 
 * <ul class='spaced-list'>
 *    <li>
 *       Instead of throwing {@link MissingResourceException}, the {@link #getString(String)} method
 *       will return <js>"{!!key}"</js> if the bundle was not found, and <js>"{!key}"</js> if bundle
 *       was found but the key is not in the bundle.
 *    <li>
 *       A client locale can be set as a {@link ThreadLocal} object using the static {@link #setClientLocale(Locale)}
 *       so that client localized messages can be retrieved using the {@link #getClientString(String, Object...)}
 *       method on all instances of this class.
 *    <li>
 *       Resource bundles on parent classes can be added to the search path for this class by using the
 *       {@link #addSearchPath(Class, String)} method.
 *       This allows messages to be retrieved from the resource bundles of parent classes.
 *    <li>
 *       Locale-specific bundles can be retrieved by using the {@link #getBundle(Locale)} method.
 *    <li>
 *       The {@link #getString(Locale, String, Object...)} method can be used to retrieve locale-specific messages.
 *    <li>
 *       Messages in the resource bundle can optionally be prefixed with the simple class name.
 *       For example, if the class is <code>MyClass</code> and the properties file contains <js>"MyClass.myMessage"</js>,
 *       the message can be retrieved using <code>getString(<js>"myMessage"</js>)</code>.
 * </ul>
 * 
 * <h5 class='section'>Notes:</h5>
 * <ul class='spaced-list'>
 *    <li>
 *       This class is thread-safe.
 * </ul>
 */
public class MessageBundle extends ResourceBundle {

   private static final ThreadLocal<Locale> clientLocale = new ThreadLocal<>();

   private final ResourceBundle rb;
   private final String bundlePath, className;
   private final Class<?> forClass;
   private final long creationThreadId;

   // A map that contains all keys [shortKeyName->keyName] and [keyName->keyName], where shortKeyName
   // refers to keys prefixed and stripped of the class name (e.g. "foobar"->"MyClass.foobar")
   private final Map<String,String> keyMap = new ConcurrentHashMap<>();

   // Contains all keys present in all bundles in searchBundles.
   private final ConcurrentSkipListSet<String> allKeys = new ConcurrentSkipListSet<>();

   // Bundles to search through to find properties.
   // Typically this will be a list of resource bundles for each class up the class hierarchy chain.
   private final CopyOnWriteArrayList<MessageBundle> searchBundles = new CopyOnWriteArrayList<>();

   // Cache of message bundles per locale.
   private final ConcurrentHashMap<Locale,MessageBundle> localizedBundles = new ConcurrentHashMap<>();

   /**
    * Sets the locale for this thread so that calls to {@link #getClientString(String, Object...)} return messages in
    * that locale.
    * 
    * @param locale The new client locale.
    */
   public static void setClientLocale(Locale locale) {
      MessageBundle.clientLocale.set(locale);
   }

   /**
    * Constructor.
    * 
    * <p>
    * When this method is used, the bundle path is determined by searching for the resource bundle
    * in the following locations:
    * <ul>
    *    <li><code>[package].ForClass.properties</code>
    *    <li><code>[package].nls.ForClass.properties</code>
    *    <li><code>[package].i18n.ForClass.properties</code>
    * </ul>
    * 
    * @param forClass The class 
    * @return A new message bundle belonging to the class.
    */
   public static final MessageBundle create(Class<?> forClass) {
      return create(forClass, findBundlePath(forClass));
   }
   
   /**
    * Constructor.
    * 
    * <p>
    * A shortcut for calling <code>new MessageBundle(forClass, bundlePath)</code>.
    * 
    * @param forClass The class 
    * @param bundlePath The location of the resource bundle.
    * @return A new message bundle belonging to the class.
    */
   public static final MessageBundle create(Class<?> forClass, String bundlePath) {
      return new MessageBundle(forClass, bundlePath);
   }
   
   private static final String findBundlePath(Class<?> forClass) {
      String path = forClass.getName();
      if (tryBundlePath(forClass, path))
         return path;
      path = forClass.getPackage().getName() + ".nls." + forClass.getSimpleName(); 
      if (tryBundlePath(forClass, path))
         return path;
      path = forClass.getPackage().getName() + ".i18n." + forClass.getSimpleName();
      if (tryBundlePath(forClass, path))
         return path;
      return null;
   }
   
   private static final boolean tryBundlePath(Class<?> c, String path) {
      try {
         path = c.getName();
         ResourceBundle.getBundle(path, Locale.getDefault(), c.getClassLoader());
         return true;
      } catch (MissingResourceException e) {
         return false;
      }
   }

   /**
    * Constructor.
    * 
    * @param forClass The class using this resource bundle.
    * @param bundlePath
    *    The path of the resource bundle to wrap.
    *    This can be an absolute path (e.g. <js>"com.foo.MyMessages"</js>) or a path relative to the package of the
    *    <l>forClass</l> (e.g. <js>"MyMessages"</js> if <l>forClass</l> is <js>"com.foo.MyClass"</js>).
    */
   public MessageBundle(Class<?> forClass, String bundlePath) {
      this(forClass, bundlePath, Locale.getDefault());
   }

   private MessageBundle(Class<?> forClass, String bundlePath, Locale locale) {
      this.forClass = forClass;
      this.className = forClass.getSimpleName();
      this.bundlePath = bundlePath;
      this.creationThreadId = Thread.currentThread().getId();
      ClassLoader cl = forClass.getClassLoader();
      ResourceBundle trb = null;
      try {
         trb = ResourceBundle.getBundle(bundlePath, locale, cl);
      } catch (MissingResourceException e) {
         try {
            trb = ResourceBundle.getBundle(forClass.getPackage().getName() + '.' + bundlePath, locale, cl);
         } catch (MissingResourceException e2) {
         }
      }
      this.rb = trb;
      if (rb != null) {

         // Populate keyMap with original mappings.
         for (Enumeration<String> e = getKeys(); e.hasMoreElements();) {
            String key = e.nextElement();
            keyMap.put(key, key);
         }

         // Override/augment with shortname mappings (e.g. "foobar"->"MyClass.foobar")
         String c = className + '.';
         for (Enumeration<String> e = getKeys(); e.hasMoreElements();) {
            String key = e.nextElement();
            if (key.startsWith(c)) {
               String shortKey = key.substring(className.length() + 1);
               keyMap.put(shortKey, key);
            }
         }

         allKeys.addAll(keyMap.keySet());
      }
      searchBundles.add(this);
   }


   /**
    * Add another bundle path to this resource bundle.
    * 
    * <p>
    * Order of property lookup is first-to-last.
    * 
    * <p>
    * This method must be called from the same thread as the call to the constructor.
    * This eliminates the need for synchronization.
    * 
    * @param forClass The class using this resource bundle.
    * @param bundlePath The bundle path.
    * @return This object (for method chaining).
    */
   public MessageBundle addSearchPath(Class<?> forClass, String bundlePath) {
      assertSameThread(creationThreadId, "This method can only be called from the same thread that created the object.");
      MessageBundle srb = new MessageBundle(forClass, bundlePath);
      if (srb.rb != null) {
         allKeys.addAll(srb.keySet());
         searchBundles.add(srb);
      }
      return this;
   }

   @Override /* ResourceBundle */
   public boolean containsKey(String key) {
      return allKeys.contains(key);
   }

   /**
    * Similar to {@link ResourceBundle#getString(String)} except allows you to pass in {@link MessageFormat} objects.
    * 
    * @param key The resource bundle key.
    * @param args Optional {@link MessageFormat}-style arguments.
    * @return
    *    The resolved value.  Never <jk>null</jk>.
    *    <js>"{!!key}"</js> if the bundle is missing.
    *    <js>"{!key}"</js> if the key is missing.
    */
   public String getString(String key, Object...args) {
      String s = getString(key);
      if (s.length() > 0 && s.charAt(0) == '{')
         return s;
      return format(s, args);
   }

   /**
    * Same as {@link #getString(String, Object...)} but allows you to specify the locale.
    * 
    * @param locale The locale of the resource bundle to retrieve message from.
    * @param key The resource bundle key.
    * @param args Optional {@link MessageFormat}-style arguments.
    * @return
    *    The resolved value.  Never <jk>null</jk>.
    *    <js>"{!!key}"</js> if the bundle is missing.
    *    <js>"{!key}"</js> if the key is missing.
    */
   public String getString(Locale locale, String key, Object...args) {
      if (locale == null)
         return getString(key, args);
      return getBundle(locale).getString(key, args);
   }

   /**
    * Same as {@link #getString(String, Object...)} but uses the locale specified on the call to {@link #setClientLocale(Locale)}.
    * 
    * @param key The resource bundle key.
    * @param args Optional {@link MessageFormat}-style arguments.
    * @return
    *    The resolved value.  Never <jk>null</jk>.
    *    <js>"{!!key}"</js> if the bundle is missing.
    *    <js>"{!key}"</js> if the key is missing.
    */
   public String getClientString(String key, Object...args) {
      return getString(clientLocale.get(), key, args);
   }

   /**
    * Looks for all the specified keys in the resource bundle and returns the first value that exists.
    * 
    * @param keys The list of possible keys.
    * @return The resolved value, or <jk>null</jk> if no value is found or the resource bundle is missing.
    */
   public String findFirstString(String...keys) {
      if (rb == null)
         return null;
      for (String k : keys) {
         if (containsKey(k))
            return getString(k);
      }
      return null;
   }

   /**
    * Same as {@link #findFirstString(String...)}, but uses the specified locale.
    * 
    * @param locale The locale of the resource bundle to retrieve message from.
    * @param keys The list of possible keys.
    * @return The resolved value, or <jk>null</jk> if no value is found or the resource bundle is missing.
    */
   public String findFirstString(Locale locale, String...keys) {
      MessageBundle srb = getBundle(locale);
      return srb.findFirstString(keys);
   }

   @Override /* ResourceBundle */
   public Set<String> keySet() {
      return Collections.unmodifiableSet(allKeys);
   }

   /**
    * Returns all keys in this resource bundle with the specified prefix.
    * 
    * @param prefix The prefix.
    * @return The set of all keys in the resource bundle with the prefix.
    */
   public Set<String> keySet(String prefix) {
      Set<String> set = new HashSet<>();
      for (String s : keySet()) {
         if (s.equals(prefix) || (s.startsWith(prefix) && s.charAt(prefix.length()) == '.'))
            set.add(s);
      }
      return set;
   }

   @Override /* ResourceBundle */
   public Enumeration<String> getKeys() {
      if (rb == null)
         return new Vector<String>(0).elements();
      return rb.getKeys();
   }

   @Override /* ResourceBundle */
   protected Object handleGetObject(String key) {
      for (MessageBundle srb : searchBundles) {
         if (srb.rb != null) {
            String key2 = srb.keyMap.get(key);
            if (key2 != null) {
               try {
                  return srb.rb.getObject(key2);
               } catch (Exception e) {
                  return "{!"+key+"}";
               }
            }
         }
      }
      if (rb == null)
         return "{!!"+key+"}";
      return "{!"+key+"}";
   }

   /**
    * Returns this resource bundle as an {@link ObjectMap}.
    * 
    * <p>
    * Useful for debugging purposes.
    * Note that any class that implements a <code>swap()</code> method will automatically be serialized by
    * calling this method and serializing the result.
    * 
    * <p>
    * This method always constructs a new {@link ObjectMap} on each call.
    * 
    * @return A new map containing all the keys and values in this bundle.
    */
   public ObjectMap swap() {
      ObjectMap om = new ObjectMap();
      for (String k : allKeys)
         om.put(k, getString(k));
      return om;
   }

   /**
    * Returns the resource bundle for the specified locale.
    * 
    * @param locale The client locale.
    * @return The resource bundle for the specified locale.  Never <jk>null</jk>.
    */
   public MessageBundle getBundle(Locale locale) {
      MessageBundle mb = localizedBundles.get(locale);
      if (mb != null)
         return mb;
      mb = new MessageBundle(forClass, bundlePath, locale);
      List<MessageBundle> l = new ArrayList<>(searchBundles.size()-1);
      for (int i = 1; i < searchBundles.size(); i++) {
         MessageBundle srb = searchBundles.get(i);
         srb = new MessageBundle(srb.forClass, srb.bundlePath, locale);
         l.add(srb);
         mb.allKeys.addAll(srb.keySet());
      }
      mb.searchBundles.addAll(l);
      localizedBundles.putIfAbsent(locale, mb);
      return localizedBundles.get(locale);
   }
}